US2314218A - Safety device - Google Patents

Description

l l Patented Marr-16, 1943 1 Francis Jimerson, Athens, Pa.,

assigner to Ingersoll-Band Company, New York, N. Y., a corporation of New Jersey Y v Appueetien september s, 1942, semi Ne. 451,160

' source of pressure iluid supply. The passage 32 3 Claims.

This invention relates to motors, and more particularly to a safety device for motors of the fluid actuated type.

One object oi the invention is to prevent the operation of the motor at dangerous speeds.

Another object is to automatically effect a reduction in the pressure value of the fluid intended to drive the motor whenever the motor speed reaches a predetermined rate.

A more specic object is to automatically effect communication between the passage conveying pressure fluid to the motor and the atmosphere whenever the motor speed reaches a dangerous rate.

for connection with a conduit leading 'froma 38 for the accommodation of a throttle valve is controlled by a throttle valve 34 journaled in the handle and opensA into a supply chamber 35 in the casing 23.

The supply chamber 35 is sealed at its outer end by a plug 36 threaded thereinto and at its opposite end by a bushing 31 having a chamber 39 which controls the ow of pressure uid from the supply chamber to the piston chamber 26. The throttle valve 39 is of the reclprocatory type and is normally held in position to admit pressure fluid to the piston chamber by a spring 4l) vwhich is arranged upon a stem 4| of the plug 36 Other objects will be in part obvious and in l5 and seats against the throttle valve 39.

pari; pointed out hereinafter, i f The outlet for pressure fluid from the supply In the drawing accompanying `this speciflcachamber 35 to the motor consists of a port 42 tion and in which similar reference numerals in the Wall f the bushing 37 and iS IOCated in refer to similar parts, s such wise that it may be controlled by the throt- Figure 1 is an elevation, partly broken away, 20 tle Valve 39 The Port 42 Opens lntO an annular of a.v pneumatically operated portable grinding groove 43, inthe casing 23, encircling the bushmachine equipped with a safety device coniing 31. The annular groove 43 in turn communistructed in accordance with the practice of the cates with a Supply Passage 44 ln the Casing, and y invention, inlet passages 45 afford communication between Figure 2 is a similar view of a detail, 25 the supply passage 44 and the piston chamber 26. Figures 3 and 4 are transverse views taken Exhaust prts 46 ln the cylinder 25 conveir the through Figure 1 on the lines 3 -3 and 4 4, reexhaust fluid from the piston chamber to an spectively, and, exhaust chamber 41 in the casing whence ex- Figure 5 is an elevation of a detail taken hallSt uid may DaSS t0 the atmosphere.

through Figure 3 on the line 5 5. 30 In the arrangement shown, the throttle valve Referring more particularly to the drawing, 39 1S actuated t0 perform ltS eontlellng funethe invention is shown, for the sake. of iuustrattion by a governor 4B acting in response to the ing a. practical application thereof, as being em- Speed 0f the piston 21. The governor may be 0f bodied in a portable grinding machine havra Wel1 known type Comprising a guide member ing a pneumatically actuated motor 2| for driving 35 '49 that iS threadedly Connected t0 the trunnion a grinding wheel 22. 29 and has an aperture 50 therethrough to slid- On the side of the casing 23 of the grinding ably reeeive Si I'Od 5| Carrying a head 52 at its machine is a handle 24 for manipulating the Outer end. The IOd 5| extends into the piston machine, and in the casing 23 is a cylinder 25 2l and is encircled by a Spring 53 that seats at that is boredto provide av piston chamber 26 for 40 one end against the guide member and at its a rotary piston 21..v The piston 21 is arranged other end against a nut 54 on the rod 5| to resist eccentrlcally within the chamber 26 and carries endwise movement of the rod in an cutwarrny a plurality of radially arranged slidable vanes direction. 28 against which pressure iiuid acts for driving Within a slot 55 in the guide member 49 are the piston. On one end of the piston is a truna pair of centrifugal weights 56 of angular shape nion 29 that extends into an anti-friction bearthat are pivoted upon pins 51 seated in the guide ing 30, and on the opposite end of the piston is member and have arms 58 extending beneath the a shaft portion 3|, the free end 0f which may` head 52 to transmit 'the centrifugal movement be secured to the grinding Wheel 22l in any Well of the weights 56 to the rod for moving said rod known manner. outwardly. This movement of the rod is trans- The pressure fluid supply for operating the mitted to the throttle valve by a rocker bar 59 motor 2| is conveyed thereto by the handle 24 that seats withone end against the outer end the handle being provided with a passage 32 havof the head 52 and with its opposite end against ing its outer end threaded, as indicated by 33,' a stem 60 on the throttle valve 39. The rocker bar is mounted upon a pivot pin 6| supported by the casing and extending through the rocker bar intermediate its ends. I

'I'he rocker bar 69 is so positioned that its opposed ends will constantly seat against the head 62 and the stem 60, and the throttle valve 39 will, therefore, always be immediately responsive to any movement of the rod 6| accordingly as the rod moves endwise in response to movement of the weights 56.

In the use of machines equipped with devices for automatic-ally controlling the speed of the rotative parts, as in the example herein described, it has been found that, notwithstanding good design and careful construction, these parts may become damaged or worn to'such an extent that they fail to operate effectively so that the motor speed may accelerate to a dangerousrate.

In view of the foregoing it is contemplated to.

provide the machine with a second safety device designed to come into action at a predetermined speed of somewhat higher rate than that at which the motor normally operates. casing 23 is provided with a relief port 62 to afford communication between the supply passage 44 and the atmosphere. 'I'he relief port 62 is preferably of equal or larger flow area. than the supply passage so that it will pass most or all of the pressure fluid from the supply passage 44 and whatever pressure fluid may enter the piston chamber 26 will be insufficient to cause overspeeding of the piston 21.

The port 62 is normally closed bya. plug 63 that extends, in the present instance, into the outer end of the port 62 and has a flange 64 to cooperate with a seating surface 66 around the outer end of the port 62 for sealing said port. The plug 63 is held against the seat 65 by a bolt 66 that extends through the plug and has ahead 61 seating against the outer end thereof. The opposite end of the bolt 66 extends vinto the chamber 68 containing the governor 46 to a point near the peripheral surface of the guide member 49 and lies in the plane of rotation of said guide member. A nut 69 is threaded on the end of the bolt lying in'the chamber 68 to lock the plug in sealing position, and the body of the bolt is provided with a section 10 of reduced diameter to provide a weakened zone in the bolt immediately beneath the nut 69.

'I'he section 10, while of large enough crosssectional area to withstand the forces to which it is normally subjected, as for example the pressure of the uid in the supply passage 44 against the inner end or pressure surface 1I of the plug 63, is so proportioned that it will break readily when a blow is struck against the nut 69. In the arrangement shown the weakened section 10 lies within anaperture 12 in the casing and the. said aperture is of a length to accommodate both the weakened section 'l0 and the adjacent portion of the body of the bolt, which it substantially equals in diameter, so that the portion of the bolt To this end the Y through the plane of rotation of the guide member. They are mounted pivotally upon pins 'Il in the guide member and on the mass portions 16 of said weights are lugs 'I1 to provide seats for an endless coiled spring 16 that resists the centrifugal force of both weights 13.

The weights 13 are so positioned on the guide member 49 that their mass portions 16 constitute the leading ends in the circle of rotation of the guide member and will, therefore, serve as the impact end for striking the nut 69 to break the bolt 66, and on the trailing ends of the weights 'I3 are flatted surfaces 19 that engage the bottom surfaces 80 of the recess 'I4 for limiting the degree of outward movement of the weights As will be apparent from'the foregoing description, the speed of the motor is Vnormally controlled .by the governor 46 the weights of which will operate in accordance with variations in the speed of the motor to control the position of the throttle valve 39 and, therefore, the flow area of the port 42. In the event, however, that these devices fail to performtheir controlling functions and the motor speed is accelerated greatly, as a result, the weights 'I3 will be actuated centrifugaliy toward the bolt 66 and one of them will collide with the nut and breakthe bolt 66 at the reduced section 10.

'I'he holdingforce on the plug 65!A will thereby be released and the pressure fluid acting against the pressure surface 'H will blow the plug 63 out of the port 62.` In this way the supply passage 44 will be placed in direct communication with the atmosphere and such fluid as may thereafter flow into the piston chamber 26 will be of insufficient presure value to operate the piston at a high rate of speed.

I claim:

1. A safetydevice for a motor comprising a casing having a piston chamber and a pressure fluid supply passage for the piston chamber, a piston in the piston chamber, a relief port in the casing for the supply passage, 'a sealing member for the relief port having a pressure surface subjected to the pressure uid in the supply passage, a locking member for locking the sealing member in position to seal the relief port, and means actlying between the weakened section 10 and the plug 63 will always remain rigid in the assembled position of these parts.

'Ihe means provided for breaking the bolt at the weakened section 'l0 under certain conditions of operation' of the motor also act in response to the speed of the piston 21, in the present instance at a predetermined speed somewhat in excess of that at which the motor normally operates, and consists of a pair of centrifugal weights 13 carried by the guide member 49. The weights 16 lie in opposed recesses 14 in the peripheral surface of the guide member and are positioned to rock ing in response to a predetermined 4speed of the piston for rendering the locking member ineffective to hold the sealing member in sealing position and thereby enable the pressure fluid acting against the pressure surface to move the sealing member from its sealing position for opening the relief port.

2. A safety device for a motor comprising a casing having a piston chamber and a pressure fluid supply passage for the piston chamber, a piston in the piston chamber, a relief port in the casing for the supply passage, a sealing member for the relief port having a pressure surface subjected to the pressure fluid in' the supply passage, a locking member for locking the sealing member in position to seal the relief port, and means acting in response to a predetermined speed of the piston for breaking the locking member to release the sealing member and enable the pressure fluid acting against the pressure surface to move the sealing member from its sealing position to open the relief port.

3. A safety device for a motor comprising a for the relief port having a pressure surface subjected to the pressure fluid in the supply passage. a locking member for locking the sealing member in position to, seal the relief port and having a weakened section, and a centrifugally operated weight acting in response to a predetermined speed of the piston to strike the locking member 5 relief port.

for breaking= it at the 'weakened section and thereby release the sealing member to enable the pressure uid acting against the pressure surface to move the sealing member for uncovering the FRANCIS Af J IMERSON.

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